Polychlorotrifluoroethylene (PCTFE), this remarkable material that has garnered much attention in the field of fluoroplastics, what exactly is it? With its unique multifunctionality, it stands out among numerous plastic materials, becoming a new favorite in scientific research and industry. The fluorine element contained in its molecular structure endows it with excellent corrosion resistance, weather resistance, and insulation properties, enabling it to exhibit outstanding performance in multiple fields such as chemistry, electronics, and aerospace.
Polychlorotrifluoroethylene (PCTFE), as the earliest thermoplastic fluoroplastic researched and put into production, has permeated all aspects of our daily lives thanks to its excellent physicochemical properties. Next, we will provide a comprehensive analysis and introduction to this remarkable material from five dimensions: molecular structure, synthesis routes, outstanding performance, and wide range of applications.

I. Molecular structure

Polychlorotrifluoroethylene (PCTFE) is a homopolymer formed by the polymerization of trifluorochloroethylene monomers. In its molecular structure, fluorine and chlorine atoms are arranged around the main carbon chain, giving the polymer unique properties. The presence of fluorine atoms makes the polymer chemically inert, while chlorine atoms contribute transparency, thermoplasticity, and hardness. Therefore, PCTFE is a thermoplastic resin that exhibits excellent performance in terms of stability, heat resistance, non-flammability, non-hygroscopicity, air impermeability, and inertness.

II. Performance

Polychlorotrifluoroethylene (PCTFE), as a high-performance polymer, possesses excellent physical and chemical properties. The fluorine atoms in its molecular chain endow it with outstanding weather resistance, heat resistance, corrosion resistance, and good insulation. Furthermore, PCTFE exhibits high melt viscosity and thermal stability, allowing it to maintain excellent performance even at high temperatures. These unique properties have led to the widespread application of PCTFE in various fields such as aerospace, electronics, and biomedicine.

III. Chemical Properties

Polychlorotrifluoroethylene (PCTFE) exhibits excellent chemical resistance and inertness due to its high fluorine and chlorine content. At high temperatures, it is only corroded by molten alkali metals or chlorosulfonic acids. Notably, the presence of chlorine atoms results in relatively poor molecular symmetry for PCTFE, which ironically gives it superior transparency, processability, and creep resistance compared to PTFE.

IV. Thermal stability

Polychlorotrifluoroethylene (PCTFE) possesses specific thermal properties. Its glass transition temperature ranges from 71 to 99°C, while its melting point is between 211 and 216°C. Notably, when the temperature exceeds 310°C, PCTFE decomposes in an oxygen-rich environment, generating compounds such as -CF, CFCF2CFCl, and CF2CCl2.

V. Mechanical Properties

By replacing some of the fluorine atoms in polytetrafluoroethylene (PTFE) with chlorine atoms, its mechanical properties can be significantly improved, including enhanced tensile strength, compressive strength, and extended creep residence time. Highly crystalline PCTFE exhibits greater brittleness, leading to reduced impact strength and elongation at break; while low-crystalline PCTFE exhibits better toughness. Furthermore, the study by BROWN et al. revealed the tensile and compressive behavior of PCTFE at different temperatures and strain rates, showing significant asymmetry, and these properties are strongly dependent on ambient temperature and strain rate. When the temperature exceeds Tg, the mechanical toughness of PCTFE is significantly improved. On the other hand, ZHANG's research found that as the temperature decreases, the hardness and elastic recovery rate of PCTFE samples increase, while the compression ratio shows the opposite trend.

VI. Dielectric Properties

PCTFE, with its excellent properties of wide bandwidth, low dielectric constant, and low dielectric loss, has shown broad application potential in high-frequency communications. HARA's research reveals that the dielectric properties of low molecular weight PCTFE are significantly affected by the crystalline region and end-group dipole interaction. Meanwhile, SCOTT et al. explored the dielectric relaxation behavior of PCTFE under low-frequency conditions, observing three distinct dielectric loss peaks in highly crystalline PCTFE. These peaks are closely related to losses on the surface of the spherulite, the movement of molecular chain segments in amorphous regions, and the recombination of defects within crystalline regions, respectively. Furthermore, Song Hangling et al.'s research further found that the crystalline morphology of PCTFE has a significant impact on its high-frequency dielectric properties; PCTFE with low crystallinity and smaller crystal size typically exhibits lower dielectric constants and dielectric losses.

VII. Barrier Performance

PCTFE exhibits excellent barrier properties, with a water vapor transmittance of only 171 kg/(mh), far superior to other plastic materials, making it the best water vapor barrier material currently available. Simultaneously, PCTFE also has relatively low absorption rates for infrared and ultraviolet light, allowing some PCTFE film products to achieve light transmittance as high as 90%.

VIII. Current Status of Application and Production

The excellent performance of PCTFE has enabled it to be used in a variety of special applications. Based on its structural characteristics, we divide PCTFE into three categories and will discuss them separately.

1. Lubricating grease grade PCTFE

Lubricating grease grade PCTFE, often referred to as fluorochlorofluorocarbon oil, stands out for its excellent chemical stability and lubricating properties. It is particularly suitable for high-temperature environments or highly corrosive and oxidizing applications, such as as a lubricant, pressure transmission fluid, or damping fluid.

2 Product-grade PCTFE

Product-grade PCTFE can be used long-term in a temperature range of -196 to 125°C, making it ideal as a corrosion-resistant and pressure-resistant sealing material, electrical insulation material, and observation window material. In the early days of the nuclear energy industry, it was widely used as an important corrosion-resistant material. Furthermore, in the semiconductor field, product-grade PCTFE has also found widespread application due to its excellent mechanical properties and corrosion resistance. Simultaneously, its excellent low-temperature resistance and creep resistance make it perform well in environments such as liquid nitrogen, liquid oxygen, and liquefied natural gas, and it can even be used in conditions close to absolute zero. Therefore, product-grade PCTFE occupies an important position in low-temperature resistant and corrosion-resistant pump and valve components.

Currently, Daikin Industries' Neoflon series products are the mainstream industrial-grade PCTFE on the market. Several Chinese companies also provide similar products, such as Jiayuan's newly developed film.

3 Thin-film grade PCTFE

Next, we will discuss the applications and properties of thin-film grade PCTFE. Currently, commercially available PCTFE films on a large scale mainly come from Daikin Industries of Japan and Honeywell of the United States. Our company develops films in three types based on different thicknesses . These films are primarily used as protective layers for packaging electrical components, solar collectors, and displays, as well as encapsulation materials for electroluminescent components. Film No. 1 is a homopolymer PCTFE product used as a barrier layer for pharmaceutical, chemical, and personal care product bottles. Film No. 2 is mainly used for pharmaceutical packaging. In addition, we also offer modified PCTFE film product No. 3 , which is copolymerized with vinylidene fluoride and suitable for automotive fuel lines and chemical packaging.

Figure: CTFE monomer copolymer membrane